U.S. patent number 7,770,617 [Application Number 11/958,158] was granted by the patent office on 2010-08-10 for safety workbench having double-walled floor trough.
This patent grant is currently assigned to Thermo Electron LED GmbH. Invention is credited to Olaf Broemsen, Edmund Frickel, Christoph Noll.
United States Patent |
7,770,617 |
Broemsen , et al. |
August 10, 2010 |
Safety workbench having double-walled floor trough
Abstract
The present invention relates to a safety workbench having a
working inner chamber enclosed by a housing, whose bottom terminus
is formed by a floor trough and which is accessible on a housing
front side via a work opening closable using an adjustable front
pane. The floor trough is implemented as double-walled and has an
internal and an external wall, which enclose an intermediate
chamber, which may be placed under vacuum, between them, at least
one of the walls having at least one opening which is connected to
means for generating the partial vacuum.
Inventors: |
Broemsen; Olaf (Moerfelden,
DE), Frickel; Edmund (Gruendau, DE), Noll;
Christoph (Gruendau, DE) |
Assignee: |
Thermo Electron LED GmbH
(DE)
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Family
ID: |
39110730 |
Appl.
No.: |
11/958,158 |
Filed: |
December 17, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080150405 A1 |
Jun 26, 2008 |
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Foreign Application Priority Data
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Dec 21, 2006 [DE] |
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10 2006 060 712 |
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Current U.S.
Class: |
144/286.5;
144/285 |
Current CPC
Class: |
B08B
15/023 (20130101) |
Current International
Class: |
B25H
1/00 (20060101) |
Field of
Search: |
;144/285,286.1,286.5,287
;108/33 ;312/209 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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44 41 784 |
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May 1996 |
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DE |
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297 23 636 |
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Jan 1999 |
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DE |
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100 17 196 |
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Oct 2001 |
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DE |
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102 14 158 |
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Oct 2003 |
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DE |
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102 17 903 |
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Oct 2003 |
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DE |
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10214158 |
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Oct 2003 |
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DE |
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10 2004 032 454 |
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Jan 2006 |
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DE |
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102004032454 |
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Jan 2006 |
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DE |
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1348497 |
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Oct 2003 |
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EP |
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6601730 |
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Aug 1967 |
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NL |
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Other References
European Search Report dated Mar. 5, 2008, pp. 2. cited by
other.
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Primary Examiner: Self; Shelley
Attorney, Agent or Firm: Wood, Herron & Evans, LLP
Claims
What is claimed is:
1. A safety workbench having a working inner chamber enclosed by a
housing, the working inner chamber having a bottom terminus formed
by a floor trough and the working inner chamber being accessible on
a housing front side via a work opening, the work opening being
closable by an adjustable front pane, wherein the floor trough is
double-walled and has an internal wall and an external wall
enclosing an intermediate chamber which is placed under partial
vacuum, each of the internal wall and the external wall having an
inclined floor plate and a plurality of side walls extending
upwardly from the floor plate, and at least one of the internal and
external walls has at least one opening which is operatively
connected to means for generating the partial vacuum.
2. The safety workbench according to claim 1, wherein the means for
generating the partial vacuum is a fan of the safety workbench.
3. The safety workbench according to claim 1, wherein the at least
one opening is situated in the external wall of the floor
trough.
4. The safety workbench according to claim 1, wherein the at least
one opening is attached to the side of the floor trough facing away
from the housing front side.
5. The safety workbench according to claim 1, wherein an intake
connecting part is attached to the at least one opening of the
floor trough.
6. The safety workbench according to claim 1, wherein the floor
trough has at least one outlet for draining liquid collected on the
internal wall, the outlet penetrating the internal and external
walls in such a way that the intermediate chamber is not open to
the outside.
7. The safety workbench according to claim 1, wherein measurement
means operatively coupled to the intermediate chamber are provided
for determining a partial vacuum in the intermediate chamber.
8. The safety workbench according to claim 7, wherein a safety
monitoring device is provided which compares a pressure measured
value ascertained by the measurement means to a stored comparison
value or comparison value range and triggers at least one of a
visual or acoustic alarm in the event of a deviation of the
pressure measured value ascertained by the measurement means and
the stored comparison value or comparison value range.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority of German patent application no.
10 2006 060 712.0, filed Dec. 21, 2006, the disclosure of which is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
The present invention relates to a safety workbench having a
working inner chamber enclosed by a housing, whose lower terminus
is formed by a floor trough and which is accessible on a housing
front side via a work opening closable using an adjustable front
pane.
BACKGROUND OF THE INVENTION
Safety workbenches fulfill various functions. They are used above
all for protecting the operator from direct exposure to infectious
aerosols, protecting the immediate laboratory surroundings from a
contamination by released aerosols (environmental and personal
protection), and protecting the product and the materials used from
contamination by microorganisms from the surroundings.
The basic construction of safety workbenches comprises an inner
chamber enclosed by a housing, which has a work opening on the
housing front side, which is closable by a transparent front pane
which is adjustable upward and/or downward. The inner chamber is
also identified in the meaning of the present invention as a
working chamber or a working inner chamber. Such safety workbenches
are already known in greatly varying embodiments from the prior
art, for example, from DE 44 41 784 A1, DE 102 17 903 C1, DE 297 23
636 U1, and DE 100 17 196 A1.
Furthermore, safety workbenches have a floor trough in the lower
section of the working chamber. Floor troughs of this type
terminate the working chamber on the bottom with a seal, capture
substances seeping through the work plate, and are to prevent the
substances from unintentionally escaping to the outside and
contaminating the surroundings of the safety workbench. A floor
trough of the prior art is described, for example, in DE 102 14 158
A1. The floor trough is shaped from a one-piece metal sheet and is
accordingly single-walled.
For the safety workbenches, it is important above all that harmful
substances or bacteria from the inner chamber of the workbench do
not reach the room where it is installed under any circumstances.
Protecting the operators and the environment is in the foreground.
Safety workbenches in laboratories, in particular those which are
suitable for microbiological work, therefore have to meet strict
safety requirements. They have fans which generate directed air
flows and guide these air flows via special filters, to remove
particles or aerosols entrained in the air and not permit them to
reach the operator or outside the safety workbench. Such a safety
workbench is described, for example, in DE 10 2004 032 454 A1.
So-called personal protection in safety workbenches is achieved by
suctioning outside air through the work opening into the working
chamber of the safety workbench. As long as this external air flow
is not obstructed and sufficient air is suctioned in, particles and
aerosols may not reach the outside from the inner chamber of the
safety workbench. The suctioned external air thus forms an air
curtain flowing through the work opening, which protects the person
working at the safety workbench and/or the environment from
contamination by the particles. A pressure reduced in relation to
the pressure in the surroundings of the safety workbench exists
inside the working inner chamber of the safety workbench due to the
flow guiding, which is also referred to as a partial vacuum in the
following. The partial vacuum ends at the surface of the floor
trough, which forms the lower terminus of the working inner
chamber, facing toward the working chamber.
To ensure that no leaks arise in the area of the floor trough,
corresponding model testing is typically absolutely required for
the licensing of the safety workbench. However, this does not
preclude that leaks will occur in the area of the floor trough in
the course of use, which are possibly no longer recognized. This
may represent a significant hazard to the operating personnel and
the environment.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a
safety workbench in which the risk of occurrence of contamination
through a damaged floor trough in the surroundings of the safety
workbench is significantly reduced in relation to the prior art and
is entirely precluded as much as possible.
This object is achieved by the safety workbench according to Claim
1. Further embodiments are described in the subclaims.
The present invention accordingly relates to safety workbench
having a working inner chamber enclosed by a housing, whose bottom
terminus is formed by a floor trough and which is accessible on a
housing front side via a work opening closable using an adjustable
front pane. The floor trough is implemented as double-walled
according to the present invention and has an internal wall and an
external wall, which enclose an intermediate chamber, which may be
placed under partial vacuum, between them, at least one of the
walls having at least one opening which is connected to means for
generating the partial vacuum.
For the prevention of leaks in the area of the floor trough, it has
been proven to be an advantage in relation to the prior art in the
implementation according to the present invention that the
double-walled implementation offers doubled safety in relation to
the single-walled floor trough, because two walls must be
penetrated here before harmful material may reach the outside from
the working inner chamber. If the inner wall is damaged,
contaminants are captured in the external wall which receives the
internal wall.
The internal wall is received in the external wall in such a way
that an intermediate chamber, which may be placed under partial
vacuum, is enclosed between the two walls. At least one opening,
which is connected to means for generating a partial vacuum, is
provided in at least one of the walls. Except for the at least one
opening for applying the partial vacuum, the internal and external
walls thus form a closed structure. The intermediate chamber is,
except for the at least one opening, completely enclosed by the
internal and external walls. If the means for generating the
partial vacuum is put into operation, a partial vacuum thus forms
in the intermediate chamber. If contaminants nonetheless reach the
intermediate chamber as a result of damage to the floor trough,
their exit from the intermediate chamber into the surroundings of
the workbench is at least made more difficult and typically
entirely prevented. The contaminants may be withdrawn from the
intermediate chamber by the means for generating the partial vacuum
and fed to a purification device, which removes the contaminants
from the withdrawn air.
The means for generating the partial vacuum are not especially
restricted in principle. For example, they may be a pump or a fan.
It is advantageous to use partial vacuum generation means which are
already present in any case in the area of the safety workbench as
the partial vacuum generation means. For example, the intermediate
chamber of the floor trough may be attached via the at least one
opening to an exhaust air system, which removes and filters the
room air at the installation location. If desired, a filter may
also be interposed between the opening of the floor trough and the
exhaust air system. It is especially advantageous to use a fan
already present in the safety workbench as the means for generating
the partial vacuum.
Typically an exhaust air fan, which conveys air via a filter to the
outside from the safety workbench, and, in addition, in safety
workbenches of class II, a circulation air fan, which circulates
the air inside the safety workbench to generate the so-called down
flow in which air is blown in the working inner chamber from top to
bottom in the direction toward the work surface and
cross-contamination (contamination from one processed sample to
another) is thus prevented, are provided as fans in safety
workbenches. The air conveyed by the fans out of the working inner
chamber is typically first withdrawn through openings in the work
surface and into a rear area of the safety workbench via the
surface, facing toward the working inner chamber, of the floor
trough situated below the work surface. The air is conducted there
through a channel which is formed behind a rear wall, which
terminates the working inner chamber to the rear, opposite the work
opening. The channel runs from bottom to top in the direction
toward the fan typically situated above the working inner
chamber.
This configuration suggests itself and is preferred according to
the present invention if the at least one opening of the floor
trough to which the partial vacuum is applied is connected to one
of the areas of the ventilation system of the safety workbench
impinged by partial vacuum, in particular using the channel behind
the working inner chamber described above. Therefore, the at least
one opening of the floor trough is preferably also situated in its
rear area--i.e., facing away from the housing front side. The
position of the opening is not fundamentally restricted further,
however, and it may be provided both in the internal wall and also
in the external wall. Because of the better accessibility, however,
the at least one opening is typically preferably provided in the
external wall. An intake connecting part may be provided over the
opening for easier connection.
The shape, size, number, and attachment location of the opening are
expediently selected in such a way that a sufficient partial vacuum
is achieved in the intermediate chamber, which expediently extends
into all areas of the intermediate chamber. With a large floor
trough, a spatial distribution of the openings over the area of the
floor trough may be advisable. Otherwise, the cited properties are
not subject to any special restriction.
The floor trough itself may--except for the double-walled
implementation and the attachment of the at least one opening to
achieve a partial vacuum in the intermediate chamber--be
implemented in a typical way. It is advisable to implement the
floor of at least the internal wall as inclined, so that the liquid
collected in the floor trough runs down to a lowest point. An
outlet may be situated there in a way known per se, through which
the collected liquid may be drained out of the floor trough. The
outlet is expediently led downward through the internal and
external walls in such a way that there is no opening in the floor
trough to the intermediate chamber which endangers the
implementation of the partial vacuum. A pipe is preferably led
through the internal and external walls, whose external
circumference the internal and external walls adjoin tightly. The
pipe may be closed at its bottom end using a cock, a valve, or in a
similar way.
The implementation of the floor trough according to the present
invention reliably prevents contaminants from unintentionally
escaping to the outside in this area and contaminating the
surroundings of the safety workbench. Even if the wall of the floor
trough is damaged, the double-walled implementation and the
application of a partial vacuum to the intermediate chamber prevent
disadvantages to user and surroundings. It is especially
advantageous that means according to the present invention may be
provided to establish damage of the floor trough. For this purpose,
for example, measurement means may be provided, which measure the
partial vacuum in the intermediate chamber. These measurement means
may comprise any typical pressure meter and may be a barometric
cell, which is either situated in the intermediate chamber itself
or in proximity to one of the partial vacuum openings of the floor
trough. If one of the walls of the floor trough is damaged, the
pressure rises in the intermediate chamber. This is established by
the measurement means. A comparative value may be stored in a
safety monitoring device, as is typically provided in a safety
workbench, which fixes a specific pressure in the intermediate
chamber as a setpoint value. If a comparison unit in the safety
monitoring device establishes a deviation from this setpoint value,
an alarm signaling device is caused to output a visual and/or
acoustic alarm. The visual alarm may not only be output by a
blinking light or a similar device, but rather a corresponding
warning message may also be output on a display which is also
typically provided in any case, which notifies of damage to the
floor trough, so that it may be repaired. Instead of a punctual
comparison value, a comparison value range may also be stored to
permit certain harmless pressure oscillations in the intermediate
chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is explained in greater detail in the
following for exemplary purposes on the basis of drawings. Only one
preferred exemplary embodiment is described, to which the present
invention is not restricted, however.
FIG. 1 schematically shows a safety workbench according to the
present invention having a floor trough in a side view.
FIG. 2 schematically shows the floor trough from FIG. 1 in a
perspective illustration.
FIG. 3 schematically shows a view of the floor trough from FIG. 1
in a cross-section A-A.
FIG. 4 schematically shows a view of the floor trough from FIG. 1
in a cross-section B-B.
FIG. 5 schematically shows a view of the floor trough from FIG. 1
in a longitudinal section C-C.
DETAILED DESCRIPTION
FIG. 1 shows a safety workbench 1, as may be used for
microbiological work, for example. The working inner chamber 3 of
the safety workbench 1 is enclosed by a housing 2. A front pane 5
is attached to the housing front side 4 of the safety workbench 1,
which may be adjusted in such a way that work may be performed on
samples in the working inner chamber 3. The samples may be placed
on a work level 7, which is provided with air slots 8. Contaminated
air is withdrawn from the working inner chamber 3 through air slots
8, led further below the work level 7 to the rear in the direction
of a channel 11, which runs from bottom to top and is separated
from the working inner chamber, and finally suctioned in by the fan
12. Before leaving the safety workbench 1, the contaminated air is
conducted over a filter (not shown here) to remove the
contaminants. The air leaving the safety workbench is replaced by
ambient air, which enters through the work opening 6. The entering
air flow prevents contaminants from exiting.
A floor trough 9 is situated below the work level 7 in such a way
that it terminates the working inner chamber 3 from below in
relation to the surroundings of the safety workbench 1. Damage to
the floor trough 9 harbors the danger that contaminants will reach
the surroundings of the safety workbench directly. To reduce this
danger, the floor trough 9 is implemented as double-walled
according to the present invention. This may be inferred from FIGS.
2 through 5. The double-walled floor trough 9 comprises an inner
wall 9a, which is inserted into a larger external wall 9b. Both
walls are permanently connected to one another around their
circumference on their upper edges and form a completely closed
structure, except for one opening 10. An intermediate chamber 17,
which extends practically over the entire area of the floor trough,
is formed between the walls.
The opening 10, which provides the only access to the intermediate
chamber 17, is located in a rear area of the external wall 9b
facing away from the housing front side 4. An intake connecting
part 18 is connected to the external wall via the opening 10. This
intake connecting part 18 opens into the channel 11 of the
ventilation system of the safety workbench 1. If the fan 12 is
operated, a partial vacuum arises in the intermediate chamber 17
due to the air flow from bottom to top in the channel 11 and thus
away from the opening 10. If, because of damage to the internal
wall 9a, material from the working inner chamber 3 passes via the
openings 8 in the work level 7 and through the wall 9a, the
material does not immediately exit unobstructed into the
surroundings of the safety workbench 1. Rather, it is captured in
the external wall 9b, withdrawn from there out of the intermediate
chamber 17 and fed to the filtration devices of the safety
workbench. There is only a serious danger that the surroundings of
the safety workbench will be contaminated when both walls 9a and 9b
are penetrated. The danger is also reduced here, however, because a
partial vacuum still exists in the intermediate chamber 17 and
contaminants may thus not exit completely unobstructed.
To be able to notice damage to the floor trough 9 or other faults
of the partial vacuum in the intermediate chamber 17, the partial
vacuum is expediently monitored. For this purpose, the partial
vacuum is measured using a pressure meter such as a barometric cell
13, which is situated directly at the outlet of the intake
connecting part 18 here. The pressure measured values, which may be
measured continuously or at predefined intervals, are transmitted
to a safety monitoring system 19, as is typically provided in
safety workbenches. The pressure measured value is compared there
to a comparison value or comparison value range, which defines the
permissible pressure or pressure range in the intermediate chamber.
If the measured value deviates from the comparison value or
comparison value range--for example, because the pressure has risen
as a result of damage to the floor trough--the safety monitoring
system outputs a visual and/or acoustic alarm. For example, a
notification may be output on a display that the pressure in the
floor trough is too high and the floor trough has to be
checked.
The shape of the floor trough also largely corresponds to shapes
typical up to this point for floor troughs of safety workbenches.
The internal wall 9a has a rectangular floor plate 16 here and side
walls 15 projecting vertically above this plate or inclined
outward. The floor plate 16 is inclined downward and to the left
toward the housing front side 4. The opening for an outlet 14 is
thus located at the lowest point of the internal wall 9a. The shape
of the external wall 9b corresponds to that of the wall 9a, but is
enlarged in relation thereto. The outlet 14 is formed by a
cylindrical pipe which penetrates the internal and external walls
9a, 9b and projects downward on the bottom side of the wall 9b. The
pipe is closable using a cock. It opens into a capture system for
disposing of contaminated waste, for example. In order that the
partial vacuum in the intermediate chamber 17 is not canceled out,
the external and internal walls are attached tightly to the
external circumference of the pipe.
The floor trough may also be produced in a typical way from all
materials used up to this point for this purpose, with the proviso
that they are suitable for producing the double-walled structure.
The floor trough preferably comprises metal, especially
corrosion-resistant metal such as stainless steel in particular.
The floor and side walls may be manufactured from individual parts
or by bending from larger sheets. The joints of the edges and
corners of the floor trough sheets are bonded to one another by a
soldering, welding, or laser method, for example.
* * * * *